block/backup: Fix hang for unaligned image size
When doing a block backup of an image with an unaligned size (with
respect to the BACKUP_CLUSTER_SIZE), qemu would check the allocation
status of sectors after the end of the image. bdrv_is_allocated()
returns a result that is valid for 0 sectors in this case, so the backup
job ran into an endless loop.
Stop looping when seeing a result valid for 0 sectors, we're at EOF then.
The test case looks somewhat unrelated at first sight because I
originally tried to reproduce a different suspected bug that turned out
to not exist. Still a good test case and it accidentally found this one.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/block/backup.c b/block/backup.c
index 7978ae2..d0b0225 100644
--- a/block/backup.c
+++ b/block/backup.c
@@ -307,7 +307,7 @@
BACKUP_SECTORS_PER_CLUSTER - i, &n);
i += n;
- if (alloced == 1) {
+ if (alloced == 1 || n == 0) {
break;
}
}
